Control system



- R. E. HELLMUND.

CONTROL SYSTEM.

APPLICATION HLED NOV. 25, 1914.

1 3 1 7,292 Patented Sept. 30, 1919.

INVENTOR RddolpbE. Hellmund.

- ATTRNEY- UNITED STATES OFFICE.

RUDOLF E. HELLMUND, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO WEST- INGHOUSE ELECTRTC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

CONTROL SYSTEM.

Specification o! I ette'rs Patent.

Patented Sept. 30, 1919.

Applicationfiled November 25, 1914. Serial No. 873,918.

To all whom it may concern: I

Be it known that I, RUDOLF E. HELLMUND, a subject of the German Empire, and a resident of Pittsburgh, in the county of Allegheny and State of'Pennsylvania, have invented a new and useful Improvement in Control Systems, of which the following is a specification. it

My invention relates to systems of control, and it has special reference to means for obviating flash-over conditions in electric railway motors and the like.

In direct-current electric railway systems, when the supply circuit energy is suddenly resumed after a temporary interruption, such as that occasioned by passing over a section break, the rush of current readily effects a building up of fluxin the laminated armature core, but the solid steel por tion of the frame that is usually included in the magnetic ,field circuit causes eddy currents to arise and, therefore, an equally rapid building up of the field flux is not efl'ected. The armature ampere-turns thus momentarily predominate over thefield ampereturns to such an extent as to cause an unduly high voltage between the commutator segments of the motor and, in some cases, to even cause flash-over of the machine. The remedy resides in eflecting anadditional increase of field current at the instant of resumption of the supply-circuit energy to prevent this excess ratio, of armature to field ampere-turns.

The object ofmy present invention is to provide a simple and inexpensive means for reliably and efiectively preventing the occurrence of flash-over conditions in electric motors by automatically effecting a term porary increase of field current upon the resumption of supply-circuit energy after a temporary interruption thereof.

According to my invention, I provideinductive means, preferabl a transformer, having its secondary winding adapted to influence the excitation of the motor field magnet winding andhaving its primary winding connected in circuit with the motor armature to receive energy from the directcurrent supply circuit, thus normall producing a substantially negligible e ect on the secondary winding, but whereby, upon.

a sudden resumption of supply circuit energy after a temporary interruption thereshunt field windin of, the transformer secondary winding is energized from the primary. winding to effect an instantaneous increased excitation of the field winding. My invention may be employed in various ways. may comprise the use of a'secondary transformer winding in either parallel or series relation to the main motor field winding or the use of a motor-generator set to excite the field Winding, the secondary transformer winding being suitably connected in the of the motor or meretor. In this way, t e main motor fiel winding is suitably energized upon the resumption of supply-circuit energy and irrespective of the rate of buildingof flux from the motor current, and thus f ash-over conditions are effectively prevented. 1

In the accompanying drawing, Figure 1 is a diagrammatic view of a system of control embodying my invention; and Fi s. 2, 3 and 4 are similar views of modifie systems that also embody my invention.

Referring to Fig. 1, the s stem here shown it concerns my present invention, may be briefly set forth as follows: The motor is started preferably with the switch C occupying its open position, whereby the secondary winding S of the transformer "is deenergized and the primary winding P,

through which current normally flows in the direction of the corresponding solid arrow, has substantially negligible eflect upon the secondary winding, inasmuch as the changes in the motor current occur at a relatively slow rate, as compared with the current variations that would be effected by the flow of alternating current in the transformer primar winding, as will be understood; Aftert e motor has been accelerated to a predetermined speed in any suitable manner, which it is not deemed necessary Such a system to describe in detail here, the switch may be closed to connect the secondary winding ing solld arrow, and, the field strength of the motor being weakened, the motor specd increases a predetermined amount, in accordance with familiar princ ples.

Assuming that the supply circult energy is interrupted and then suddenly resumed shortly afterward, the motor armature flux will build up at a greater rate than the field flux, as hereinbefore ointed out, and a certain amount of flux wi 1 be mmediateliy created by the current in the primary win ing P of the transformer. A correspondlng opposing or counter-flux Wlll also mmediately be set up in the secondary winding S of the transformer to send a current therethrough in the direction of the dotted arrow, which current is added to the slmultaneous initial field winding current to suitabl increase the field strength of the motor an thereby prevent the flash-over conditions hereinbefore mentioned.

Reference may now be had to Fig. 2 of the drawing, in which is shown a system comrising the supply-circuit conductors Troley and Ground, a motor having an armature A and a field winding F, a transformer T and a motor-generator set, coupled in any suitable manner, as by a shaft 8,-the generator armature G of which is adapted to ener- 86 gize the field winding F, which, 1n this case, is

not included in the same circuit as the armature A, and the motor armature M of which is adapted to be energized from a suitable storage batter B or other convenient source of energy. he motor of the motorenerator set is provided with a shunt eld winding MF, the strength of which may be varied by a suitable resistor R, and the generator is provided with'a I shunt' field winding GFl and a second field wind n GF2 that is connected in series relation wit 1 the armature A and the primary winding P of the transformer.

The Fpurpose of the auxiliary field wind-.

ing G 2, which, .in the present system and also in those to be subsequently described, is energized in accordance with the mainarmature or load current, is to so sup lement the action of the auxiliary shunt eld winding GFl as to render the e'nergization of the main field winding F normally dependent upon variations of such load current. Upon the resumption of supply-circuit energy, aftera temporary interruption thereof, the previously-described inherently sluggish action of the main field winding tends to prevent such normal action for a short time, during which initial period, the transformer. T acts to temporarily effect the desired energization of the main field windposing flux to build u ing F in the same directionf'as the normal excitation upon an increaseof the-load current, as more fully set'forthbelow.

Assumin the system to be n0rmally operating with current flowing 1n the respective clrcuits in the directions-indicated by the arrows, the operation of the, system, with respect to the obviation of flash-over conditions, may be described as follows: as in the case shown in Fig. 1, the primary winding P of the transformer normall "has substantially negligible effect upon t e secondary winding S,- but when the supply circuit energy is suddenly resumed, after a-temporary interruption, the relatively great instantaneous change in the flux emltted b the primary winding P sets up a correspon ing 'and opposing flux in the secondary winding S which thereby acts in effect as an additional source of electromotive-force in the circuit of the main motor field wind-' ing F, consequently increasing the field strength of the main motor to a predetermine degree.

Another system for accomplishing the same object is illustrated in Fig. 3, the apparatus employed being identical withthat shown in Fig. 2, but the secondary transformer winding S is connected in circuit.

with the shunt field winding MF of the motor-generator set in such a way as to receive a current that flows in the same directlon as the current in the primary winding P, as indicated by the solid arrows.

Upon a sudden resumption of supply-circult energy after a temporary interruption thereof when the systemillustrated is normally operating, the sudden chan e of flux in the primary winding P of t e transformer sets up an opposin flux in the secondary windin S, as in ica ted by the dotted arrows, w ich flux thus serves to weaken the current flowing through the shunt field winding MF of the motor generator. The speed of the set is thereby correspondin 1y increased to also increase the voltage de ivered by the generator armature G, and, consequently, the field strength of the main motor field winding F.

Still another system for effecting the desired object is illustrated in Fig. 4, wherein the secondary winding S of the transformer T is connected in series relation with the shunt field winding. GFl of the generator G, the remainder of the system comprising the same apparatus as that illustrated in Fig. 2 and Fig. 3. The currents in the various circuits normally flow in the directions indicated by the respective arrows.

When the supply-circuit energy is suddenly resumed, after being temporarily interrupted, the flux created in the primary winding-P causes a corresponding and opin the secondary winding S, whereby t e current flowing.

i through the generator shunt field winding mined degree. 1

Although it is true that the-shunt field GFl 1s correspondingly increased, and the generator armature voltage, together with the current flowing in the main motor field winding F that is connected across the armature G, are also increased to a Winding of a dynamo-electric machinemay be consldered as indirectly dependent upon,

or energized in accordance with, the load current of the machine, I desire 1t to be understood that such a construction is to -ergized in accordance with the load cur-'- be considered as excluded by the claims that specify a fieldwinding normally enrent. 1

winding and having its primary winding- I do not wish to be restricted to. the specific circuit connections or arrangement of parts herein set forth, .as' modifications-3 thereof may obviously be made within the spirit and scope of my invention. I desire,

therefore, that only such limitations shall" be imposed as are indicated in the appended claims. v I claim as my invention: 1. In a a system of 'control, the combination with a directcurrent supplycircuit, and

a dynamo-electric machine having an arma ture and a field magnet winding, of an auxiliary motor-generator set having its generator connected to excite saidfield-magnet wihding, and a transformerhaving its secondary winding associated with said motor-generator set in such manner as to influence the excitation of said field-magnet connected in series-circuit relation with said armature to the supply circuit and normally producing substantiall negligible effect on said 'secondarywin ing for eflecting an increased excitation of the field-mag net winding upon a sudden resumption of supply-circuit energy, after a temporary interruption thereof.

2. In a system of control, the combination with a dynamo-electric machine having an armature and a main field-magnet winding, a motor-generator set having the 'generator thereof connected to excite said. field predeteran auxiliary motor-generator having winding, and an auxiliary source of energy adapted to energlze the motor of said motorgenerator set, ofva transformer having the primary windin connected in series with the armature 0 thesfirst mentioned machine and the secondary windin connected in series with the main field winding forpreventing abnormal ratio of armature ampere-turns to field-windingampere-turns upon the resumptionof supply-circuit energy after temporary interruption thereof.

3. In a-system of control, the combination with a dynamo-electric machine having an armature and a field-magnet winding, of its generator element connected to. excite said field magnet winding, and a transformer o having its secondary winding associated withsaid motor-generator in'such manner as to influence the excitation of said field magnet winding and having its primary ",Inagnet winding, ,of' an "auxiliary motorgenerator having its generator element connected to excite said field-ma et winding, an auxiliary source of energy or energizing the motor element of said n1otor-generator,

and a transformer having its secondary winding associated with said motor-generator in such manner as toinfluence the excitation of said field-magnet winding and hav: ing its primary winding connected in seriescircuit relation with, said armature and adapted to produce a I field-ex'citation-increasing effect upon the secondary winding under predetermined abnormal conditions. In testimony .whereof, I have hereunto subscribed my name this 19th day of Nov.,'

,Witnesses:

A. J. BRooMAL B. B..H1NEs.'

RUDOLF E. HELLMUND. f 

